Bill,
A lot depends on which type of coupon you actually have, as there are two types. There is the one hour mentioned by you, normally sent to all Select members, available from AGR by trading points for them, and even found on EBay for sale. Then there is a two day coupon sent out to Select Plus members only.
Obviously the latter is much easier to use, especially these days with record ridership on Acela. One also needs to be flexible in one's travel to have a better chance at using either of the coupons. For example, you can pretty much forget about using the one hour coupons on a Friday night and even the two day coupons can sometimes be impossible to use on Friday nights. You'll also find that it's easier to use the coupons between NYP and BOS, by comparison to NYP-WAS.
I've personally used both many times but again, one has to watch what one books in order to use them.